Information is communicated in a communication system between two or more communications stations. Information which is to be communicated between the communication stations is transmitted upon a communication channel formed to extend between the communication stations. In a two-way communication system, a communication station includes both a transmitter and a receiver operable to transmit and to receive, respectively, communication signals. Thereby in a two-way communication system, information is both transmitted and received at a single communication station.
A radio communication system is a communication system in which the communication channel formed between the communication channels is a radio channel defined upon a portion of the electromagnetic spectrum.
A radio communication system inherently increases communication mobility as communication channels defined in such a system are formed of radio channels and do not require wireline connections to form the communication channels. A radio communication system, however, typically is bandwidth-limited. That is to say, regulatory bodies which allocate usage of the electromagnetic spectrum allocate only a limited amount of the electromagnetic spectrum for communications in a particular radio communication system. Because the spectrum allocation for use by a particular system is limited, communication capacity increase of a radio communication system is limited by such allocation. Efforts are made, therefore, to construct a radio communication system in manners which efficiently utilize the allocated spectrum.
A PCS, or other mobile communication system is exemplary of a radio communication system. Mobile communication systems make relatively efficient use of the spectrum allocated thereto. Signals generated during operation of the mobile communication system are of relatively low power levels. Because of the use of low-power signals, the same channels can be reused throughout a mobile communication system according to a cell reuse plan. Concurrent use of the same channels is permitted according to the cell reuse plan, thereby to effectuate concurrent communications on the same channels by different communication station pairs at different locations throughout the area encompassed by the mobile communication system.
However, even with the relatively efficient utilization of the allocated spectrum, many mobile communication systems have been operated at their maximum capacities, particularly at certain-times-of-day and within certain cells of the mobile communication system. With technological advancements and the need to address the capacity problems of conventional mobile communication systems, various mobile communication systems have been developed which permit increased capacities of communication therein.
In many instances, the mobile communication systems of such increased capacities require the installation of separate network infrastructures and the construction of separate mobile stations to be operable to communicate therewith. The separate network infrastructure are commonly overlaid upon existing mobile communication systems. And, mobile systems constructed according to different communication standards have been installed also in non-overlapping geographical areas. That is to say, different types of mobile communication systems are installed in different geographical areas. A mobile station operable pursuant in only one of the systems is operable only in the geographical area encompassed by such system.
Dual-mode mobile stations, for instance, are available to permit a user to communicate alternately by way of two different mobile communication systems. More generally, multi-mode mobile stations have been developed to permit their operation in multiple different mobile communication systems. Such dual- and multi-mode mobile stations typically must include circuitry specifically constructed for each of the different mobile communication systems in which the mobile station is operable. The various communication systems, for instance, are operable at different frequency bands, with different modulation schemes, with different coding schemes, etc. Therefore, conventional dual- and multi-mode mobile stations are sometimes to include separate, but functionally redundant, circuit paths for each of the communication systems in which the mobile station is to be operable.
Such duplication increases the complexity of the mobile station as well as the costs of the mobile station. And, because the redundant circuit paths each require separate circuit elements, the physical size of the resultant mobile station increases.
However, different ones of the mobile communication system standards sometimes exhibit some commonalities. For instance, the same modulation schemes are utilized but at different frequency ranges. Or, different modulation schemes might be utilized in the different communication systems but at the same range of frequencies.
For instance, an analog system such as AMPS (Advanced Mobile Phone System) is operable at a frequency range located about 800 MHz and utilizes an FDMA (Frequency Division Multiple Access) method. This system utilizes frequency modulation techniques to modulate information which is to be communicated during its operation. A digital systems such as PCS (Personal Communication System) which is operable at a frequency range of about 1.9 GHz utilizes various access methods, including a CDMA (code division, multiple-access). CDMA systems generally utilize QPSK (Quadrature Phase Shift Keying) modulation technique. Therefore, this same modulation technique is also utilized for CDMA systems operable at the cellular band of frequencies, i.e., the range located at about 800 MHz.
If advantage could be taken of the commonality of the different systems in which a multi-mode mobile station is to be operable, sharing of circuitry portions of the different circuit branches could be made. Such sharing would reduce the cost of the mobile station, along with permitting a reduction in the physical dimensions of the resultant mobile station.
It is in light of this background information related to radio devices, such as mobile stations operable in mobile communication systems, that the significant improvements of the present invention have evolved.